1. Field of the Invention
This invention relates to bearing assemblies for bearings disposed between concentric shafts of high and low pressure rotors of a gas turbine engine and particularly to such an assembly having a titanium matrix composite support ring surrounding the outer race of the assembly.
2. Discussion of the Background Art
A conventional gas turbine engine includes a core engine having in serial, axial flow relationship, a high pressure compressor to compress the airflow entering the core engine, a combustor in which a mixture of fuel and the compressed air is burned to generate a propulsive gas flow, and a high pressure turbine which is rotated by the propulsive gas flow and which is connected by a large diameter high pressure shaft to drive the high pressure compressor. A typical bypass turbofan engine also has a low pressure turbine aft of the high pressure turbine and which drives a forward fan forward of the high pressure compressor with a low pressure shaft concentrically disposed within the first shaft.
In order for intershaft differential bearings to function properly, the bearing races must remain in contact with the bearing. Typically, the inner race is positioned on the high pressure shaft which has a higher rotational speed and, thus, the inner race undergoes a higher radial growth or deflection as compared to the outer race which as positioned on the low pressure shaft and running at a lower rotational speed. This configuration is designed to have the inner race deflect or grow more in the radial direction than the outer race and, thus, provide that the races are always engaged. In order to achieve this required bearing support, complex hardware geometry is required to support the outer race on the low pressure shaft (see U.S. Pat. No. 4,558,564 for example). The present invention is designed to eliminate much of this complex hardware, simplify the inter-shaft bearing assembly and provide that the inner and outer races are always engaged with the rolling elements therebetween.